1. Field of the Invention
The field of the invention relates to humidifiers for generating steam, and more particularly relates to heating elements used in such humidifiers.
2. Brief Description of the Related Art
Humidifiers are commonly used in residential and commercial settings to increase the level of humidity in the air for various purposes, such as health, safety and reliability. For instance, it has been found that increased humidity reduces the amount of recuperation time required for upper respiratory infections. In addition, increased humidity reduces the amount of static charge which can build up on electrostatic sensitive devices, such as semiconductors and integrated circuits.
After operating a humidifier for a period of time, the components of the humidifier must typically be cleaned in order to control bacterial growth and remove mineral deposits. Mineral deposits caused by excess minerals in solution, such as calcium in the water used to generate steam is a problem, particularly when the deposits form on a heating element used to bring the water to a boiling point.
FIGS. 1A and B show a top and side view, respectively, of a heating element of the prior art. This conventional heating element includes a mounting portion 15 and a ring 11 having an open interior section 13. The heating element is suspended in water within a boiling chamber of the humidifier. It has been found that the inner circumference of the ring 11 is particularly susceptible to the deposition of minerals, which in some cases causes a so-called "arch effect" wherein the deposited minerals create arches across the open interior section 13 of the ring 11. These arches are particularly difficult to remove by the user, and removal often mars the external finish of the heating element such that additional minerals are deposited more quickly and are even more difficult to remove.
Some of the conventional heating elements include a flattened bottom surface, which becomes a collection point for small air bubbles that are created along a lower surface of the boiling chamber and float upwards as the water is boiled. As the smaller bubbles combine to form larger bubbles under the flattened bottom surface of the heating element, these larger bubbles eventually escape and float to the top of the boiling chamber creating an undesirable noise to the user upon bursting at the top of the boiling chamber. In addition, as the larger air bubbles burst, water droplets are projected onto additional surfaces surrounding the boiling chamber. These droplets leave additional mineral deposits or scaling upon evaporating.
Still other heating elements have a horizontally disposed lower portion that transfers excessive heat from the heating element to the remaining components of the humidifier. Since in most cases much of the remaining components are either plastic or not suitable for operating at high temperatures, this creates an undesirable and often dangerous situation. In addition, the proximity between the horizontally disposed portion and the mounting portion of the heating element provides restricted cavities which are prone to mineral deposits.
Therefore, it would be advantageous if a heating element could reduce the amount of mineral deposits on and around the heating element and/or reduce the noise created by air bubbles which collect underneath the heating element.